List and insert entities, which are very widely used within KDE documentation."

KXML

KXML Editor is a KDE application, that displays and edits contents of XML file. "Main features:

Drag and drop editing, clipboard support

Use DOM level 2 Qt library parser

KParts technology support

DCOP technology support

Editing KOffice compressed files

KXML Editor 1.1.4 is [the] last version that uses Qt library XML parser. We [are] working on KXML Editor 2.x that use Xerces-C++ 3 parser."

Be advised that "At this time, this project is sleeping."

Quanta Plus

"Quanta Plus is a highly stable and feature rich web development environment...Even the way it handles XML DTDs is based on XML files you can edit. You can even import DTDs, write scripts to manage editor contents, visually create dialogs for your scripts and assign script actions to nearly any file operation in a project." Quanta Plus is included as part of the kdewebdev package.